1. Field of the Invention
The present invention relates to a display device such as a liquid crystal display device, in particular, a capacitive touch sensor that allows a user to input information by bringing a finger or the like into contact with or proximity to the touch sensor, and a display device and an electronic apparatus including such a touch sensor.
2. Description of the Related Art
Recently, attention has been paid to a type of display device which has a contact detecting device (hereinafter, referred to as touch sensor) or a so-called touch panel directly mounted on a liquid crystal display device, and in which various buttons are displayed on the liquid crystal display device instead of ordinary buttons to allow input of information. Since this technology enables shared placement of the display and buttons amid the growing tendency toward larger screen sizes of mobile apparatus, the technology provides significant advantages such as space saving and reduced number of parts. However, this technology has a problem in that the overall thickness of the liquid crystal module increases due to the mounting of the touch sensor. In particular, in mobile apparatus applications, a protective layer is necessary for protecting the touch sensor from scratches. Thus, the liquid crystal module tends to become increasingly thicker, which goes against the trend toward reduced thickness.
Accordingly, for example, Japanese Unexamined Patent Application Publication No. 2008-9750 and U.S. Pat. No. 6,057,903 each propose a liquid crystal display element with a touch sensor in which a capacitive touch sensor is formed, thus achieving reduced thickness. In this liquid crystal display element with a touch sensor, a conductive film for touch sensor is provided between the observation-side substrate of the liquid crystal display element, and a polarizing plate for observation arranged on the outer surface thereof, and a capacitive touch sensor is formed between the conductive film for touch sensor, and the outer surface of the polarizing plate, with the outer surface of the polarizing plate serving as a touch surface. In addition, for example, Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 56-500230 proposes a structure in which a touch sensor is built in a display device.